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Nematic LC material in the aligned state scatters light strongly, but in low loss LC cored fiber waveguides it scatters less and has enhanced recovery time.

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Abstract:We have investigated the nonlinear optical response of low loss Si 0.6 Ge 0.4 / Si waveguides in the mid-infrared wavelength range from 3.25-4.75μm using picosecond optical pulses. We observed and measured the three and four-photon absorption coefficients as well as the Kerr nonlinear refractive index. The dynamics of the spectral broadening suggests that, in addition to multiphoton absorption, the corresponding higher order nonlinear refractive phenomena also needs to be included when high optical pulse intensities are used at mid-infrared wavelengths in this material.

Abstract:We characterize the nonlinear optical response of low loss Si 0.6 Ge 0.4 / Si waveguides in the mid-infrared between 3.3 μm and 4 μm using femtosecond optical pulses. We estimate the three and four-photon absorption coefficients as well as the Kerr nonlinear refractive index from the experimental measurements. The effect of multiphoton absorption on the optical nonlinear Kerr response is evaluated and the nonlinear figure of merit estimated providing some guidelines for designing nonlinear optical devices in the mid-IR. Finally, we compare the impact of free-carrier absorption at mid-infrared wavelengths versus near-infrared wavelengths for these ultra-short pulses. References and links1. R. Soref, "Mid-infrared photonics in silicon and germanium," Nat. Photonics 4(8), 495-497 (2010). 2. B. Jalali, "Nonlinear optics in the mid-infrared," Nat. Photonics 4(8), 506-508 (2010). Brun, S. Ortiz, P. Labeye, S. Nicoletti, and C. Grillet, "Nonlinear optical response of low loss silicon germanium waveguides in the mid-infrared," Opt. Express 23(7), 8261-8271 (2015).